This should probably be in the Rogues’ Gallery, because there are elements of roguery visible: the cables that form a conduit for water to drip into the building for instance. But the point I want to make about this is that no aerial will work properly when it has a large amount of metal inside its capture area. The wall in this picture is, of course, metallic. An aerial’s capture area can be thought of as the invisible envelope of space around it inside which any object can affect its performance. The capture area extends perhaps 30 or 40cm above and below a UHF TV aerial. In theory it ought to be less ‘behind’ the aerial, but in practice odd effects will be noticed even when an aerial is looking directly away from the metal, as in the lower example here.